Viruses found living in new born babies' guts

In one of the first studies of its kind, researchers found viruses living in the intestines of new born babies. Till now it was thought that only bacteria invade and colonize the baby’s gut after birth.Subodh Varma | TNN | September 16, 2015, 12:59 IST

Pollutants linked to 450 percent increase in risk of birth defects (Thinkstock photos/Getty Images)In one of the first studies of its kind, researchers found viruses living in the intestines of new born babies. Till now it was thought that only bacteria invade and colonize the baby’s gut after birth.

"We were surprised that right from the beginning quite a diversity of viruses was found in the gut," said Lori R. Holtz, professor at the university's school of medicine and senior author. "It prompts the question—where do these viruses come from? We don't know yet whether diet, method of the baby's delivery or other environmental influences play a role."

The earliest stool samples were taken at 1-4 days of life, and even at this early time point, Holtz noted, viruses were present.

Analyzing genomic material in the stool samples, the researchers noted that some of the viruses they identified are known to infect cells of the human host, but others actually infect the bacteria.

In fact, the researchers found that the kinds of viruses that infect bacteria, not human cells, were the most rich and diverse earliest in an infant's life and then their numbers declined. They also showed that strains of bacteria did the opposite, starting out with low numbers early and becoming more diverse as the babies grew into their toddler years.

"We are just beginning to understand the interplay between all the different types of life within our gut," said senior author Holtz, MD, assistant professor of pediatrics. "They are not stand-alone communities. We also are seeing that the environment of the infant gut is extremely dynamic, which differs from the relative stability that has been shown in adults."

The researchers also observed a relatively large diversity of a type of virus that infects human cells called anellovirus which appear to reflect a person's immune status, with more viruses present when the immune system is weaker. Almost all of the anelloviruses identified in this study were previously unknown.

"One child had at least 47 anellovirus strains at the 12-month sampling," Holtz said. "It's important to remember that these are healthy children living in the community. We wondered if we see a wide diversity of anelloviruses at this age because the children are losing the mother's immune protection that they have had since birth, and they are still in the process of building up their own immunity in this interval."

"At this point, we're just trying to establish what is normal," Holtz said. "We don't have enough data yet to know whether a baby's virome is affected by the environment in the same way that the bacterial microbiome is—through, for example, diet, method of delivery and antibiotic use. We suspect that it is, but that hasn't been shown.